Per the Appraisal Institute of Canada's approach to condition-based adjustments, appraisers price a fixer-upper against recently sold, renovated comparables and then subtract the estimated cost to bring the home up to that same condition, plus a buffer for the uncertainty of work not yet started. That subtraction, not a flat citywide percentage, is what separates a fixer-upper's price from a move-in-ready one.
Move-in-ready homes also tend to attract more competing offers, since they qualify for financing more easily and appeal to buyers who do not want a renovation project on top of a move, which adds its own upward pressure on price beyond the cost of materials and labour alone.
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